I love my Garmin Edge 305. It produces alot of information which I track via software on the computer. Between it and the software I am able to see where i went, where I went fast, where I got the best workout and the software is even able to congregate the info. I like to look at my calories per week and my miles per month (for the 500 mile month thread here).
In the past I've set and met a goal of 7k calories a week (7000 calories = 2 lbs of fat). Now I'm just working on the 500 miles per month.
I started at about 250 lbs last spring and I'm down to 198 now. Can't say this is due to the cyclometer but it sure has helped.